1. Technical Field of the Invention
The present invention relates to an apparatus for controlling the amount of waste heat of an engine, which apparatus controls an amount of waste heat of an engine based on a request for utilizing heat.
2. Related Art
An engine installed in a vehicle generates combustion energy when fuel is combusted. The combustion energy includes lots of heat energy other than kinetic energy used for traveling of the vehicle. Heating of a vehicle cabin, warming-up of a catalyst, and the like are performed using this heat energy. For example, there is a well-known configuration in which the waste heat of an engine included in the engine cooling water is recovered and heating is performed utilizing the recovered waste heat.
There is also a well-known method of controlling combustion energy as disclosed in JP-A-H05-215000 and JP-A-H05-059936. According to this control, the ignition timing and the valve on-off timing of the intake/exhaust valves are controlled during the engine operation. The amount of waste heat of the engine is increased under this control to accelerate warming-up of the engine and the catalyst.
However, there is a concern that change of ignition timing and valve timing for increasing the amount of waste heat of an engine may deteriorate the fuel consumption of the engine. In this regard, the controlling method described in the above patent documents does not take account of the deterioration in the fuel consumption accompanying the change of ignition timing, and the like. Therefore, from the viewpoint of fuel-consumption performance, this method may not necessarily be an optimum method as a means for increasing the amount of waste heat of an engine.
Further, there is another well-known method of controlling combustion energy as disclosed in JP-A-H11-324746. According to this control, similar to the above control, the ignition timing and the valve on-off timing of the intake/exhaust valves are controlled to thereby raise the temperature of the exhaust gas. Thus, the catalyst can be warmed up at an earlier stage.
However, the change of ignition timing and valve timing to increase the amount of waste heat of an engine may cause abrupt change of the engine torque. Therefore, there is a concern that the drivability may resultantly be deteriorated.